Ask HN: What marketing books/courses helped you to learn digital marketing?

As a software engineer, I find that the approach for learning marketing seems quite different from learning programming. In marketing, the feedback loop is longer and the certainty of what's wrong is not as clear as we have in programming thanks for the compilers. Moreover, by the own nature of the field, seems hard to discern and find the good content from the "scammy" or useless content. If you are a software engineer, that learned digital marketing and consider yourself decent at it, what resources did you use to learn? How was your journey?